Coral reefs in the climate crisis: How synbio could use symbiotic relationships to build stronger ecosystems

4 min read

Written by Claire Pinckney

February 19, 2024

Adapted from:

In the discussion of climate change’s impacts on our world, you’ve likely heard plenty about coral reefs. The increasing temperatures caused by greenhouse gases are heating up our oceans and damaging the coral. The microalgae that live in these coral reef systems flee when the heat becomes deadly for them, causing the coral to ‘bleach’, or, in other words, die due to a lack of nutrients. Even if you really care about the ocean, you may still wonder— how far do the impacts of coral reef heating and bleaching go? And what does synthetic biology have to do with it?

A post from The Reef-World Foundation says it all best. Beyond housing 25% of all marine life, coral reefs are vital to the economy through coastal fisheries and tourism, they protect coastlines from harsh conditions for people and animals alike, and they’re a gold mine for medical research. Now that we’ve established the importance of coral reefs, it’s clear why the damage and death that heat and bleaching thrust upon them is dangerous. Bueger et al. approached solving this problem with a microalgae that commonly lives in symbiosis with coral, which shows promise for synthetic biology applications in the future.

Making stronger friendships

Symbiosis is when two organisms live together in a relationship, whether neutral, good, or bad, and in this case, synthetic biology will be enhancing the good. Within one of the parties of this symbiotic relationship, there can be another relationship existing within the organism, called endosymbiosis. Coral and microalgae are in a symbiotic relationship where the coral’s structure protects the microalgae and the microalgae provides energy via photosynthesis for the coral to grow itself. However, under too much heat, the microalgae will leave and cause bleaching in the coral.

Bueger and his team decided to work on the microalgae because they are fast at reproducing and responsible for providing nutrients to the coral. Once changed, they can quickly reproduce and spread the change across the coral reef systems they’re a part of.

To evolve the microalgae, Bueger and his team used exposure to heat over 4 years to get the microalgae to adapt to warmer temperatures through building natural resilience - kind of like how you might get someone to overcome their fears by facing them.

Next, a pleasant discovery was made. In testing the heat-exposed microalgae against normal microalgae, not only did they survive and function better in the heat than their non-evolved counterparts, but three microalgae strains also produced less reactive oxygen species— the chemicals which lead coral to bleach! Not only did the team find a way to protect coral from the rising temperatures, they also found a way to protect the coral from the microalgal response to heat with three particular microalgae strains.

Working together

Finally, to put it all together, the modified microalgae were introduced into coral larvae and subjected to warmer conditions (31°C) again as they grew. It was found that coral gained the benefits of functioning and growing normally at higher temperatures from their symbiotic relationship with the microalgae. One strain of microalgae in particular, dubbed ‘SS8’, showed especially good results because of its uniquely effective response to warmer conditions.

As is true with most science there is still more research to be done. Can the coral and microalgae survive properly when temperatures drop outside of summer, or are they only capable of working in warmth? What’s their longevity? These are a couple of the questions raised by Bueger et al., but one more could come to mind: What if we genetically modified the microalgae instead of ‘training’ it to be heat tolerant?

Genetically-enhanced teamwork

While it’s still extremely important to tackle climate change at the source, synthetic biology helps ecosystems adapt to the changes that have already resulted from it. Synthetic biology is all about modifying organisms to adapt to new conditions. Think of it like enforcing a beneficial genetic mutation and significantly speeding up what would come through luck after years of evolution. So what if we could use this knowledge to help coral to persist in warmer conditions, and even resist bleaching? Instead of heat training microalgae repeatedly over time, we could use the heat tolerant microalgae as a blueprint to modify microalgae to do exactly as we need, like becoming resilient to year round temperatures.

However, these possibilities are still early in testing, as synthetic biology is a quickly developing but relatively new field. Research on using synthetic biology for coral is something to keep an eye out for in our near future!